Broadband folded h-plane orthogonal tee

ABSTRACT

An H-plane folded Hybrid Tee having E and H arms on a substantially central common axis, the termination of the region common to all arms being a substantially continuous solid wall connecting a narrow wall of the E-arm with a wide wall of the Harm on the side opposite the conjunction with the folded arms, said solid wall being discontinuous only to the extent of integrally cast matching structure.

United States Patent Salzberg l l BROADBAND FOLDED H-PLANE ORTHOGONAL TEE Nov. 4, 1975 Primary Exarm'ner-Paul L. Gensler Attorney, Agent, or Firm-Thomas N. Tarrant [76] Inventor: Edward Salzberg, 19 Black Oak Rd, Wayland, Mass. 01778 22 Filed: Aug. 26, 1974 1 ABSTRACT 21 App| 500 452 An H-plane folded Hybrid Tee having E and H arms on a substantially central common axis, the tennination of the region common to all arms being a substanl52l 333/1]; 333/98 R tially continuous solid wall connecting a narrow wall [51] Int. Cl. H01? 5/20 of the E arm with a wide wall of the H on the Side [58] Fleld 0 Search 333/ll opp0site the conjunction with h folded arms Said solid wall being discontinuous only to the extent of in- [56] References and tegrally cast matching structure.

UNITED STATES PATENTS 3,375.472 3/1968 Walker .3 333/11 7 Clams 5 Drawmg figures US. Patent NOV.4, 1975 3,918,011

BROADBAND FOLDED H-PLANE ORTHOGONAL TEE BACKGROUND OF THE INVENTION:

l. Field of the Invention:

The present invention relates to waveguide hybrid tees and particularly to broadband I-I-plane folded tees having their E and H arms on a substantially central common axis.

2. Description of the Prior Art:

A discussion of hybrid tees can be found in Micro wave Engineering, by A. F. Harvey, published by Academic Press, Inc. of New York City in 1963 at pages H7, 118 and 119. The usual configuration of the H- plane tee is two main anns in line, a shunt H-arm and a series Earm. This is shown at the top of page H8 in Microwave Engineering. The main arms may also be folded in the forked" configuration, shown in FIG. 3.l7(c) on the same page, so that the two main arms share a common narrow wall. The term orthogonal has been applied to junctions in which the shunt H-arm has been folded to place it parallel with the axis of the series E-arm while the two arms remain rotated 90 with respect to each other. The series E-arm and the shunt H-arm can thus have a common central axis or have their axes parallel but offset. The common central axis for E and H arms is shown in Purcell's junction FIG. 3.l8(b) on page 119 of Microwave Engineeringv More recently, R. M. Walker, et al have described the orthogonal arrangement applied to the hybrid tee in US. Pat. Nos. 3,192,489 and 3,375,472. The Walker et al patents describe a cavity behind the boundaries of the opposed E and H arms opposite the conjunction with the main arms as part of the matching structure. This cavity is reduced substantially below the width of the rest of the common region to prevent propagation of the TE mode thus simplifying matching problems. In order to obtain broadband performance, Walker discloses in US. Pat. No. 3,375,472 a series of inductive posts following the path of a usual H-plane bend. Broadband is defined as having similar band width characteristics to the waveguide alone.

SUMMARY OF THE INVENTION In accordance with the present invention, an H-plane folded hybrid tee of the orthogonal variety is provided that has broadband performance without a cavity ex tension or the addition of inductive posts. Thus, the inventive junction is more compact and may be made with all elements integrally cast. Looking in along the axis of the two main arms, the matching structure in the common region is comprised of steps progressively re ducing the narrow dimension to zero starting at a point just beyond the leading edge of the E-arrn opening and ending just in front of the trailing edge of the H-arm opening. The trailing edge of the H-arm opening is connected to the trailing edge of the E-arm opening with a solid, preferably slanting wall. A bulge formed in the slanting wall adjacent to the E-arm opening provides inductive tuning for the E-arm port while a central constriction in the H-arm port provides capacitive tuning for the H-arm port.

Although a lot of theory could be hazarded as to why the present tee performs as it does, it is more a result of empirical serendipity than mathematical analysis. Component parts of different prior configurations were juggled to obtain a common axis orthogonal design that would meet required performance characteristics.

While this juggling of parts was performed in a judicious and knowledgeable manner, the broadband results were not anticipated. Thus, it is an object of the present invention to provide a novel broadband folded H-plane orthogonal hybrid tee of compact and economical design.

This and other objects of the present invention will become apparent upon reading the following disclosure together with the drawing.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. I is a perspective view ofa hybrid tee according to the invention.

FIG. 2 is a bottom plan view of the tee of FIG. I. FIG. 3 is a left side elevation of the tee of FIG. 1. FIG. 4 is a section taken along 44 of FIG. 1.

FIG. 5 is a section taken along 5-5 of FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

While the inventive tee can be scaled to operate at desired frequencies, present work is on an X-band device and the Drawing depicts such a device on a one to one scale. It will be recognized that the depicted embodiment includes integral standard flanges which are not part of the invention and would not be scaled when scaling the device to different frequencies. The standard flange sizes are in many cases a detriment to the compactness inherent in the present tee since the size of the flanges dwarfs the device itself.

For purposes of flexibility it should also be borne in mind that the folded main arms are frequently cast or otherwise formed separately. This permits them to be made in different lengths, with bends, terminating in flanges or terminating in diode switches or other desired configuration. For purposes of description, a short length of folded main arms 10 is depictedv In the perspective view of FIG. I, integral standard flange 11 carrying E-arm port 12 obscures most of the interior. The right hand edge of the E-arm port, I2, as shown in FIG. 1 is connected to the right hand edge of the H-arrn port, I4, by sloping wall 16 depicted better in FIG. 4. Inductive ridge 17 is a small integral ridge across sloping wall 16 just below the opening of E-arm port 12. Upper wall 18 of folded main arms 10 is shown extending to the left and connected to the common region of the four arms immediately below and inside the left edge of flange 11.

The bottom view of FIGv 2 depicts capacitive ridge 15 as being only about as wide as the narrow dimension of the waveguide. It may be substantially flush with bottom flange 19 as shown in FIG. 4. On each side of the aperture for the E-arm port, 12, in common region 20, the narrow dimension of the common region cavity is progressively reduced by steps 21, 22 and 23 of which 21 is the farthest from the plane of view and 23 is the nearest being just below flange I9.

FIG. 1 also shows the eflect on the exterior casting of the internal configuration. Thus, steps 2], 22 and 23 produce the exterior stair effect 25. Flange lips 27 and 28 are reduced in thickness where main arms 10 connect as shovm in FIG. I when the main arms are not integrally cast. This permits a good joint in fitting them together as well as providing a perfect inside cover for bolt holes that have to be drilled in that part of the flanges.

FIG. 3 shows a left side elevation with the main arms removed to provide a better interior view of common region 20. It will be seen in the figure that a central portion of region 20, having the approximate width of the narrow waveguide dimension, is clear of obstructions other than inductive ridge 17. Most of the remaining interior width of the common region is progressively reduced in height toward the far edge of the H-arm port where it reaches zero. The remainder of the width of common region 20 is slightly narrowed starting even with first step 21 by thickening sidewalls 30 and 31.

This narrowing of the common region at the location of the steps reduces the wide dimension of region 20 to a width more than half the wide dimension of main arms but less than the entire wide dimension of main arms I0. Common narrow wall 32 of main arms 10 is preferably spaced from the nearest edge of the E-plane arm (port 12) by 0.2l6 wavelengths.

In the cross section elevation FIG. 4, common narrow wall 32 of main arms 10 is depicted as hatched and that it is cut back so that a portion of the far wall of main arms 10 extends farther into common region 20. Small lip 35 facing capacitive ridge 15 at the bottom of sloping wall 16 has additional (capacitive) effect. A small recess 36 about the depth of waveguide wall 18 thickness extends from the interior end of waveguide wall 18 to E-arm port 12. The width of recess 36 is depicted in FIG. 5 as substantially equivalent to the narrow waveguide dimension.

It is to be understood that waveguide dimensions as referred to herein are the interior cross section dimensions of waveguide matching the four ports.

The dimensions for an exemplary X-band tee in accordance with the invention are as follows:

EXAMPLE l0.2 giguhertz center frequency) Port sizes (all) .400 x .900 in.

Distance between exterior flange surfaces .750 in.

Flange thickness (each) .l75 in.

Capacitive ridge [5 .IOO X .l75 in.

Slope of wall In 75 Width of wall 16 .400 in.

Inductive ridge l7 .l in. below flange face .125 in. thick .l65 in. extension into port opening Space between wall 32 and central axis through ports 12 and I4 .700 in.

Wall thickness at 30. 3|

increased by .l()() in.

Lip 35 .05 X .05 in.

Progressive steps (H & W):

Step :1 .145 .14nin.

Step 22 .l90 X .250 in.

Step 23 .115 x1901.

Testing a tee made in accordance with the preceding exemplary dimensions, the following voltage standing wave ratio curves were tabulated without deleterious -continued Freq.(in gigahertz) H-arm E-arm l 1.0 1.30 L27 1 LS 1.40 I. [5 12.0 1.50 l.l0 [2.4 1.75 L30 While tees of the general type may have been made to produce better wideband performance figures, it has not been accomplished with as simple and economical a structure. The tested structure was cast entirely in one piece except for the common arms and the only machining required was for mounting purposes at the several ports. Since the requirements of the project in hand were less than was produced, very little experimenting was carried out and it is anticipated that slight dimensional changes within the scope of the invention will give improved results.

Thus, while the invention has been described with respect to a specific embodiment, obvious variations within the skill of the art are contemplated and it is intended to cover the invention as set forth within the spirit and scope of the appended claims.

I claim:

1. A broadband H-plane folded hybrid tee comprismg:

a. two main anns folded so as to share a common narrow wall and having a wide dimension and a narrow dimension;

b. an E-plane arm sharing a substantially common axis with an H-plane arm, said common axis being perpendicular to a plane parallel to said wide dimension and bisecting both main arms;

0. a common region common to all arms having a wide dimension facing the wide dimension of said main arms, a narrow dimension facing the narrow dimension of said main arms; and,

d. a termination of said common region formed by a substantially continuous sloping solid wall directly connecting a narrow wall of said E-plane arm with a wide wall of said H-plane arm on the side opposite the conjunction with the main arms, said solid wall being discontinuous only to the extent of integrally cast matching structure.

2. A broadband H-plane folded hybrid tee according to claim 1 wherein said solid wall is sloped relative to said common axis and said matching structure comprises a raised inductive ridge across a narrow dimension of said E-plane arm.

3. A broadband H-plane folded hybrid tee according to claim 1 wherein said matching structure comprises an inductive ridge at said E-plane arm and a central capacitive constriction at said H-plane arm.

4. A broadband l-I-plane folded hybrid tee according to claim 1 wherein the common narrow wall of said main arms is spaced from the nearest edge of said E- plane arm by 0.216 wavelengths.

5. A broadband H-plane folded hybrid tee according to claim 1 further comprising means to progressively reduce the narrow dimension of said common region to zero on the sides of a central slot starting beyond the common narrow wall of the main arms and ending at the opposite wall of said H-plane arm.

6. A broadband H-plane folded hybrid tee according to claim 5 wherein said means to progressively reduce is a plurality of unequal steps.

3,918,01 l 6 7. A broadband H-plane folded hybrid tee according than half of said wide dimension of said main arms but to claim 6 wherein the wide dimension of said common less than the entire wide dimension of said main arms. region is reduced at the location of said steps to more 

1. A broadband H-plane folded hybrid tee comprising: a. two main arms folded so as to share a common narrow wall and having a wide dimension and a narrow dimension; b. an E-plane arm sharing a substantially common axis with an Hplane arm, said common axis being perpendicular to a plane parallel to said wide dimension and bisecting both main arms; c. a common region common to all arms having a wide dimension facing the wide dimension of said main arms, a narrow dimension facing the narrow dimension of said main arms; and, d. a termination of said common region formed by a substantially conTinuous sloping solid wall directly connecting a narrow wall of said E-plane arm with a wide wall of said H-plane arm on the side opposite the conjunction with the main arms, said solid wall being discontinuous only to the extent of integrally cast matching structure.
 2. A broadband H-plane folded hybrid tee according to claim 1 wherein said solid wall is sloped relative to said common axis and said matching structure comprises a raised inductive ridge across a narrow dimension of said E-plane arm.
 3. A broadband H-plane folded hybrid tee according to claim 1 wherein said matching structure comprises an inductive ridge at said E-plane arm and a central capacitive constriction at said H-plane arm.
 4. A broadband H-plane folded hybrid tee according to claim 1 wherein the common narrow wall of said main arms is spaced from the nearest edge of said E-plane arm by 0.216 wavelengths.
 5. A broadband H-plane folded hybrid tee according to claim 1 further comprising means to progressively reduce the narrow dimension of said common region to zero on the sides of a central slot starting beyond the common narrow wall of the main arms and ending at the opposite wall of said H-plane arm.
 6. A broadband H-plane folded hybrid tee according to claim 5 wherein said means to progressively reduce is a plurality of unequal steps.
 7. A broadband H-plane folded hybrid tee according to claim 6 wherein the wide dimension of said common region is reduced at the location of said steps to more than half of said wide dimension of said main arms but less than the entire wide dimension of said main arms. 